To date, such a device has been used, for example, for the precise and shock-resistant support of a working roller, especially of a pressure cylinder in a Flexo-rotary-printing machine. The support surfaces that are pressed against each other in working position, especially shaped as truncated cones, serve as a stop and for centering during precise positioning in working position. This precise positioning and simultaneous positive support of a pressure cylinder in relation to a counter-pressure cylinder is particularly important, since it is unavoidable in printing that impact forces in radial direction of the printing cylinder are exerted upon it. These, however, must be eliminated, since displacements of the order of magnitude of even a few hundredth millimeters affect the printed image.
In its working position, the pressure cylinder is in contact with the counter-pressure cylinder on the one hand, and with a color application roller on the other hand. During interruptions of the printing, it is necessary to pull back the pressure cylinder from the line between the color application roller and the counter-pressure cylinder, so that the plates of the pressure cylinder are separated from the color application roller and the path of the material feeding across the counter-pressure cylinder. When printing recommences, the pressure cylinder is against pushed forward into working position and must return precisely to the position it held prior to the interruption of printing, as transitory and inking errors will occur.
In the case of printing machines with several printing cylinders, in which either each printing mechanism has its own counter-pressure cylinder, or several printing cylinders are used with a common counter-pressure cylinder, it is also general practice to withdraw the pressure cylinders from contact with the counter pressure cylinder or cylinders during work interruptions. In the case of printing machines with one counter-pressure cylinder, this makes it necessary for the lower printing cylinders to be lifted into working position, while the upper printing cylinders must be lowered into working position.
In the case of prior art bearing arrangements of the type to be discussed, in which the printing cylinder is pulled back into the working position, it was initially common to retract the bearing jewel against a plane stop-surface of the bearing block in the working position. In this construction, shearing loads could be absorbed only by frictional forces between the stop surfaces of the bearing block and bearing jewel, and by support of the guide bolt in the bore of the bearing head. Because of the play necessary for the displacement of the printing cylinder between guide bolt and bore, deflection of the system was possible. Beyond this, the solution is not applicable wherever the printing cylinder must be moved into working position from the bearing block.
It has thus become common practice to provide the guide bolt of the bearing jewel with an exterior cone which, upon outward movement of the bearing jewel, comes to abut against an interior cone fastened on the bearing block around the guide bolt. This results in centering and positioning of the printing cylinder bearing, and hence the printing cylinder. A disadvantage of this construction is that, here too, impact and pressure forces exerted on the printing cylinder must be compensated for primarily by reaction-impact forces in the conical surfaces. For the purpose of supporting the printing cylinder, therefore, the sliding guide bolt can also be loaded. In the case of impact forces from changing directions, unavoidable in printing machines since the plates of the printing cylinder abut against both the path of the material at the counter pressure cylinder, and against the color application roller, play in the bearing of the guide bolt in the bore of the bearing block can increase in an undesirable manner.
The disadvantage of this prior art construction can be explained as follows: The arrangement of the conical seating surfaces permits, upon influence of radial forces on the printing cylinder, an at least approximate rotational movement about an instantaneous center located at the point of intersection of the mid-vertical of the cone surfaces. During such a rotation, assuming that, because of the very slight displacement paths, the conical seating surfaces can be considered to be spherical surfaces, pure displacement movements occur in the conical seating surfaces, so that merely frictional forces and not substantially more advantageous normal forces are available for the absorption of the shock stresses of the printing cylinder. The guide bolt therefore continues to be loaded by lateral forces, causing a displacement of the guide bolt in its guide. This condition will be further discussed below.
The object of the invention is a device of the type initially described, in which the radial forces exerted upon a shaft are absorbed not by frictional forces or by the loading of a guide that is necessarily provided with play, but primarily through normal forces. The guide bolt should conceivably be loaded in pull- or push-direction in order to produce high preload tension which forces the support surfaces against each other.
This problem is solved, according to the invention, by locating the center axis of the shaft within the smaller angle formed by the support surfaces of the bearing jewel.
The result of this solution is that the instantaneous center of a pure push-movement in the support surfaces, and the rotational axis of the shaft which is impact-stressed in the radial direction, are located on the same side of the support surfaces and, especially, even coincide. In the latter case, impact stresses cannot produce a displacement movement in the support surface, since the forces to be absorbed in the support surfaces impact the latter perpendicularly, so that the resulting impact forces can be absorbed by pure normal forces. The occurring impact forces can conceivably cause the bearing jewel to be raised from the support surfaces of the bearing block in a direction perpendicular to said surfaces. This normal movement can, however, be readily suppressed by a suitable pretensile force which is calculated to be, even in the case of extreme impact loads, greater than the forces tending to lift the bearing jewel. To produce such a pretensile force, only push- or pull-loading of the guide bolt is required, so that there is no danger of its guide being deflected.
An advantageous and rather simply executed embodiment of the support surfaces is a conical seat with straight surface lines. The surface lines need not, however, necessarily be straight; curved lines, for example circular arc lines, can also be considered. The conical seat also need not be formed as a closed circle, but can be limited to circular sections in the loading directions, since loads in the longitudinal directions of the printing cylinder practically never occur and the dimensions of the seat thus can readily be shortened in this manner.
Further, the support surfaces can have a multicornered or polygonal basic form that can also be formed only in the loading directions. A gable-shaped arrangement of the support surfaces is also possible, their contour lines preferably extending parallel to the shaft axis.
If the contour line of the support surfaces represents a doubly open multi-cornered form, an intercept line of the average vertical planes comprising a plurality of partially straight lines is produced and can be so designed that it will intersect the shaft axis at least once. At the same time it is assured that there is no instantaneous axis which is parallel to the shaft axis within a pure push-movement.
The stability of the bearing vis-a-vis impact forces increases with the vertical component of the intercept line of the mid-vertical planes. It is desirable but not necessary that the vertical component of this intercept line intercept the shaft axis, because there is no push-instantaneous axis which is parallel to the shaft axis.
In addition to the slanted support surfaces, it is possible to use further, adjoining support surfaces which extend in the opposite direction with respect to the plane which is perpendicular to the shaft axis. This results in a prismatic guide. It is also possible to arrange several such prismatic guides side by side. In this manner, several intersecting axes of mid-vertical planes are produced, effecting reciprocal displacement blockage in the support surfaces.
Other variations are possible, the only important requirement being that the shaft axis, which is stressed by radial impact forces, remain within the smaller of the angles formed by two support surfaces, so that the impact forces can be substantially absorbed by normal forces.